1. Field of the Invention
The invention relates to a vacuum chamber system for semiconductor processing.
2. Description of the Background Art
Vacuum chamber systems of the type mentioned at the outset are known in different embodiments from the prior art and are used in particular in the area of IC and semiconductor production, which has to take place in a protected atmosphere as far as possible without the presence of contaminating particles. For example, in a production plant for semiconductor wafers or liquid crystal substrates, the highly sensitive semiconductor or liquid crystal elements pass sequentially through a plurality of process chambers in which the semiconductor elements present inside the process chamber are processed by means of one processing apparatus in each case. Both during the processing inside the process chamber and during the transport from process chamber to process chamber, the highly sensitive semiconductor elements must always be present in a protected atmosphere—in particular in an air-free environment.
The prior art, for example, U.S. Pat. No. 5,076,205 or U.S. Pat. No. 5,292,393, discloses multichamber systems for the production of semiconductor elements—in particular semiconductor wafers—in which a plurality of process chambers are arranged in a star-shaped manner around a central transfer chamber. The central transfer chamber is connected via a tunnel to a second transfer chamber, around which further process chambers are arranged in a star-shaped manner, so that a large cohesive semiconductor production system can be produced by means of a multiplicity of such processing islands.
The semiconductor elements are transported from one process chamber via the transfer chamber into the next process chamber by means of a handling system arranged in the transfer chamber. The very short transport distances within a processing island constitute an advantage of this proven technology. Since the central transfer chamber as well as the process chambers can be in the evacuated state during the entire process, no complicated introduction and removal of components are required for transport.
The star-shaped vacuum chamber systems described are used for different areas of semiconductor production and have proven useful for the production and processing of small to medium-sized semiconductor components. However, new technical areas require increasingly large integral semiconductor components which require the provision of novel semiconductor production systems. Examples of this are flat screens or solar panels having a width of more than two meters. For processing such large semiconductor components, process chambers having correspondingly large dimensions are required. For a star-shaped arrangement of these process chambers in the form of a plurality of processing islands, including the respective infrastructure, an area for erection of the entire semiconductor production system is required which usually exceeds the dimensions of customary production halls, which generally have an elongated floor area too narrow for such arrangements.
The prior art also discloses vacuum chamber systems whose process chambers are arranged along a line and have openings which can be sealed vacuum-tight and point in a common direction. The known system is described below. A transfer chamber which can be moved linearly parallel to the process chamber line can be docked with the individual process chambers and serves for transporting the components from one process chamber to the next process chamber. For this purpose, the transfer chamber opening of the evacuated transfer chamber is docked vacuum-tight with a process chamber opening. The closures of the process chamber and of the transfer chamber, which in particular are in the form of slide valves, are then opened. Owing to the connection between the two evacuated spaces, the two chambers exert a considerable force relative to one another. The semiconductor components are transported by means of a conveyer apparatus, for example a handling robot, from the process chamber into the transfer chamber for transport to the next transfer chamber. After the openings have been closed and the pressure in the intermediate space increased, the semiconductor components protected in the evacuated atmosphere are brought via transfer means, which are formed, for example, by a high-precision rail system, to the next process chamber by linear displacement of the transfer chamber.
A disadvantage of this known system is that docking of the transfer chamber with the process chamber has to take place in a highly accurate manner. After docking and before opening, it must be ensured that the sealing surfaces of the process chamber and of the transfer chamber lie tightly next to one another or one on top of the other in such a way that vacuum-tight contact results after opening of the closures. Since the sealing surface between the transfer chamber and the process chamber can withstand only a certain maximum contact pressure which is well below the force caused by the mutual compression, supports which act between the chambers and appropriately limit the distance between the sealing surfaces and absorb the force are provided on the transfer chamber and/or the process chamber. When the sealing surfaces or the supports are not sufficiently precisely aligned with one another, in particular due to insufficiently precise docking, vacuum-related pressing together of the two chambers results in a relative movement until the transfer chamber is supported on the process chamber and the sealing surfaces come to rest properly one on top of the other. Either the transport chamber or the process chamber yields to this relative movement to a limited extent, for example by means of appropriately formed bearings.
Such vacuum chamber systems have been used to date especially in an experimental manner for vacuum chambers having small dimensions. Although precise alignment of the transfer chamber with the process chamber presents no problems in the case of small opening sizes and relatively low chamber weights, it was not possible to date satisfactorily to solve the problem of docking since firstly high-precision guides are required for correct alignment and secondly the use of complicated bearings is necessary for permitting the relative movement due to the vacuum-related pressing together of the chambers.
Since this problem could not be adequately solved even in the case of small to medium vacuum chamber sizes, the use of such a system appears to be ruled out in principle in spite of the potential of a more compact arrangement for large chamber systems, in particular having an opening width of more than two meters, in the case of which, owing to even greater chamber dimensions, opening sizes and chamber weights, misalignment can be ruled out even to a lesser extent than in the case of systems having smaller dimensions.